The overall goals of this PPRU grant are to establish within the Department of Pediatrics at The University of Tennessee, Memphis membership in a Network of Pediatric Pharmacology Research Units. The Department of Pediatrics is based at Le Bonheur Children's Medical Center (LBCMC), St. Jude Children's Research Hospital (SJCRH), and the Newborn Center (NBC) of the Regional Medical Center at Memphis. Utilizing the facilities and core laboratory of a State of Tennessee Center of Excellence in Pediatric Pharmacokinetics and Therapeutics (CPPT) and the facilities of an NIH-funded General Clinical Research Center at Le Bonheur, a group of established investigators of the CPPT will serve as the faculty for this unit. Established areas of expertise in the CPPT include: I) developmental differences in hepatic and renal drug disposition in immature animals as influenced by genetic polymorphisms, 2) studies on the pharmacokinetics and pharmacodynamics of intravenous vitamin D in childhood dialysis patients, 3) pharmacokinetics of atenolol therapy in Marfan's syndrome, and 4) pharmacokinetics of fentanyl in painful crises in sickle cell anemia. Two proposals for network studies are included and cover the topics of erythropoietin use in children and glutamine provision in pre-term infants receiving total parenteral nutrition. Aria Advisory Committee will meet quarterly to assess this PPRU as well as define criteria for the addition of new studies. A Safety Monitoring Committee composed of local and external advisors will review all data.